1. Field of the Invention
The present invention relates to an electronic pressure regulator that can be used for gaseous fuel control on internal combustion engines. More particularly, the present invention related to an electronic pressure regulator that has direct acting electro-mechanical operation with pressure sensor feedback.
2. Prior Art
Most of the fuel control in the world for spark ignited engines or engines in general is not electronic fuel injection. In some particular markets, mainly gaseous fuel, for example, LPG and natural gas, there are issues that make fuel injection less desirable. With LPG, it is contamination. The LPG quality in the world, especially in the United States, is not controlled very well and so you have a lot of heavy-end hydrocarbons that has equally plugged up your injectors.
A pressure regulator is a device that maintains a desired pressure quantity at a predetermined value or varies according to a predetermined plan. Most fuel pressure regulators for internal combustion engines are purely mechanical devices, have a fixed orifice and work off a diaphragm, piston, or other pressure balance mechanism. Mechanical regulators use a force balance to set orifice size based on spring force verses the difference in pressure between the inlet and outlet sides of the regulator. These regulators cannot make accommodations for variation in engine operating conditions in order to provide an optimum fuel to air mixture for gaseous fuel internal combustion engines.
Gaseous fuel means a fuel which is in the gaseous state at standard temperature and pressure. Examples of gaseous fuels used with internal combustion engines are: natural gas (derived from a liquid or compressed gas storage state), and propane/butane gas (derived from liquid petroleum gas storage).
Many internal combustion engine applications use direct fuel injection systems instead of pressure regulators and carburetors, but for engines using gaseous fuels there are some significant advantages to using a regulator and carburetor instead of fuel injectors.
Contamination. Gaseous fuels, most evident in LPG, have many contaminants that clog the small orifices in fuel injectors and cause failures, reduce component life, or increase maintenance. Regulators and carburetors do not have any small orifices that are affected by contamination from gaseous fuels.
Improved fuel and air mixture. Inadequate mixing of the fuel and air prior to combustion can lead to a decrease in fuel efficiency and an increase in engine emissions. In particular, gaseous fuel mixing with air is accomplished much better using a continuous flow device (regulator and carburetor) than with a discrete flow device (fuel injector).
In spark ignited engines, fuel can be introduced to the combustion chamber in two different states; vapor and liquid. For either of these states to be injected, the fuel must be at a higher pressure, and it must be free from contaminants that would inhibit the operation of the injector. Because of the contaminants contained in propane, injection can be problematic on propane spark ignited engines. Vapor carburetion provides a good alternative method of propane fuel introduction to the engine.
While the carburetor is designed to mix the fuel and air and adjust fuel to match the speed and load of the engine, it has only “ballpark” accuracy. This accuracy is not fine enough to achieve emissions targets. To achieve accurate fueling, the fuel pressure to the carburetor (in reference to the air inlet pressure to the carburetor) can be controlled. This is done in with the Electronic Pressure Regulator of this invention.